Linear electron beam tube having a dome shape rf window

Abstract

An electron beam tube device such as an inductive output tube of the integral cavity type has a RF window which re-enters the interaction space within the cavity thereby defining a space that is within the interaction cavity but is outside the vacuum. An output coupler in the form of an output coupling loop protrudes into this space and thus couples with the electromagnetic field within the interaction space, whilst remaining outside the vacuum envelope. This allows the coupling loop to be adjusted without any additional seal arrangement between the coupling loop and walls of the output cavity.